Flowmeters are widely used to measure rates of flow and delivery volumes of fluids.
In some positive displacement flowmeters tooth rotors are arranged on parallel axes within a sealed cavity. The rotors intermesh as fluid flows in one side, outward around both tooth rotors, and then out through an outlet. The volume of the spaces between the teeth are known, rotation of the rotors is sensed and volume and rate of flow may be determined.
Meshed helical rotors have been in use in flowmeters since at least as early as the beginning of the 20th century. However, no flowmeters have taken the unique form of the present invention.
The use of helical rotors in flowmeters has caused axial loading of the rotors, which tends to push the rotors toward one end of the housing in which they rotate. The axial loading of the rotors increases wear at the end of the housing, toward which the rotors are forced. Wear causes varied clearances at opposite ends of the housings. Changing clearances by axial force and wear changes flow-by characteristic of flowmeters and may adversely affect accuracy.
Periodic blocking of inlet ports and outlet ports causes pulsations which may reduce accuracy and which may create noise, vibrations and wear.
Needs exist for improved flowmeters with improved accuracy and wear characteristics and reduced noise.